The reflection (scattering) of light can be seen on the picture they choose to make their point. Sure, the comment is correct that anything you can see scatters light otherwise you would not see it, but in the picture it is particular obvious where the light source is from the reflection on the rock.
The only time something doesn't reflect light is if it's painted in that special black that's even darker than vanta black, because that's what makes it so black; it absorbs all light instead of reflecting any.
I used to canoe on this lake in Wales, someone had attached a buoy to a gate and chucked it in, presumably as a marker…from where our camp was, the buoy looked shiny and metallic. It was actually white and partly covered in grime. Distance does weird shit.
If it doesn't reflect light, it'd be black. If it emitted its own light then there wouldn't be shadows in the craters of the moon and we also wouldn't have moon phases. It's hard to tell if this person is actually being serious because this is literally just entry level physics. Plus, we've collected moon rocks during the numerous moon landings.